Automatic base line drift corrector device for use in an integrator for chromatographical analysis

ABSTRACT

An automatic base line drift corrector device for use in an integrator for chromatographical analysis, essentially including means for generating an instantaneous correction signal by which a correcting operation with respect to the base line value of the signal can be instantaneously carried out and means for generating a non-instantaneous correction signal by which a correcting operation with respect to the base line value of the signal can be carried out with a time lag with respect to the detected signal, either of said first and second generating means being employed by a switching means for excluding an interval between the starting and terminating points of the peak appearing in the signal in connection with the wave form or time of the signal.

United States Patent Saw [11] 3,797,300 Mar. 19, 1974 [75] Inventor:

[73] Assignee: Shimadzu Seisakusho Ltd., Kyoto City, Japan [22] Filed:Nov. 23, 1971 [21] Appl. No.1 201,396

Tatsuo Sato, Kyoto City, Japan [30] 7 Foreign Application Priority Data3,475,600- 10/1969 Spence ..73/23.1X

Primary E.taminer Richard C. Queisser Assistant ExaminerStephen A.Kreitman Attorney, Agent, or Firm-Wender0th, Lind & Ponack [57] ABSTRACTAn automatic base line drift corrector device for use in an integratorfor chromatographical analysis, essentially including means forgenerating an instantaneous correction signal by which a correctingoperation with respect to the base line value of the signal can beinstantaneously carried out and means for generating a non-instantaneouscorrection signal by which a correcting operation with respect to thebase line value of the signal can be carried out with a time lag withrespect to the detected signal, either of said first and secondgenerating means being employed by a switching means for excluding aninterval between the starting and terminating points of the peakappearing in the'signal in connection with the wave form or time of thesignal.

5 Claims, 10 Drawing Figures /NPJU7 2:

HJPILO l i i PATENTEB IIAR 19 I974 SHEET 1 0F 3 FIG. Ira) FIG. Nb)

F/G.3(a)

FIG. 4(a) FIG. 4(0) minimums mm 13797300 SHEET 3 BF 3 FIG. 9

A B C D FIG. /0

AUTOMATIC BASE LINE DRIFT CORRECTOR DEVICE FOR USE IN AN INTEGRATOR FORCHROMATOGRAPHICAL ANALYSIS The present invention relates to an automaticbase line drift corrector device for use in an integrator forchromatographical analysis adapted to automatically detect the startingpoint and terminating point of the peak in a chromatograph to integratethe area under the peak so that correction of the base line drift can beeffected without altering the wave shape or amplitude of the analyticalsignals detected. In the art of chemical analysis, chromatographs areused to analyze the chemical contents of samples and are designed so asto provide output analytical fluctuations indicative of the occurrenceand concentration of the chemical constituents. Nevertheless a propertechnique for this purpose includes the use of actual onset analysiswhich results in a higher or lower base line value. Obviously, it issometimes desirable or even necessary to alter the base line value toaccomplish various chromatographic analyses in which the analyticalsignals provided by various sensors, detectors, voltage sources or othertransducers may normally integrate the areas under respective peaks withrespect to the base line thereof. Because of the importance of obtaininganalytical signals having a base line which is essentially drift-free,and for many reasons, it has been found desirable to provide a devicefor correcting base line drift.

The correction of the base line for the chromatograph constitutes, inprinciple, instantaneously correcting to zero a point on the curve whichis above the zero point of the base line before detecting the peak. However, according to such a method, a part of the curve of the peak iscorrected to zero by a drift of the base line, when the detection of thestart of the positive slope of the peak has been delayed as shown inFIG. 1(a). The vertical axis of FIG. 1(a) and the horizontal axisthereof show the height of the peak and the time interval thereof,respectively. If the peak is wide with a gentle slope when the peakstarts at the time point A, there will be a considerable amount of timeelaspe until the slope reaches a fixed value or more. Accordingly, thedetection of the-peak is often delayed. If the peak is detected, forexample, starting at time point B, the

base line is instantaneously corrected so that the peak starts at zeroat the time point B, whereby the portion of the peak prior to the timepoint B is corrected to zero by a drift of the base line. Therefore,only the lined area of the peak between B and C is calculated by meansof an integrator. Since the peak actually ends at D a considerable erroris caused with respect to the actual area under the peak because thearea under the line B C and betweenA and D is not calculated.

Thus, a fixed time lag is generally used for the correction of the baseline and the part of the curve of the peak before the start of thecalculation of thearea under the peak is not cancelled, and the area ofthe hatched portion defined by B, E, F and C in FIG. 1(b) is calculated.

However, in such a method of correcting the base line a considerableerror is likely to be caused with respect to a peak which is difficultto separate. This is described hereinafter with reference to FIGS. 2 and3.

The vertical axis of FIGS. 2 and 3 shows the peak and the base line,respectively, while the horizontal axis thereof, shows the time. Thestart of the positive slope of the first peak is detected at point A,the end thereof being detected at point B, the start of the next peakbeing detected at point C and the end thereof being detected at point D.At first, in FIG. 2(a), it is assumed that the base line has driftedfrom the height designated at point A to the height designated at pointC when the end of the first peak has been detected at point B. In

this case, as for the second peak, the area covered with i start point Cof the next peak is short. As shown in FIG.

2(b), the base line can drift as far as point F. Accordingly, the areaunder the second peak calculated by the integrating device becomes theportion covered with the oblique lines between C, F, G and D of FIG.2(b), which is a considerably bigger size than the actual area, that is,the area of the portion covered with the-oblique lines between C and Dof FIG. 2(a). I In order to prevent the errors, as. shown in FIG. 2(b),from being caused, the area of the portion covered with the obliquelines between C and ID of FIG. 2(a) must be calculated as if theinstantaneous correction were carried out without a time lag in thecorrecting action for the base line. However, in this case, 'aconsiderable error is caused with respect to the'type of peak shown inFIG. 3.

FIGS. 3(a) and 3( b) show the case where the second peak is produced onthe negative slope of the first big peak, in which condition, as shownin FIG. 3(a), the respective areas of the portions, defined by A, E andB and C, and D have to be calculated. However, if the correction of thebase, line is carried out instanta' neously after the-slope of the firstpeak has become a longer than the time interval between B and C of FIG.

3(a), and is actuated after the lapse of the predetermined time.

However, the area can not be calculated correctly by any conventionalmethod for the curves of both FIG. 2(a) and FIG. 3(a).-Either the area.of FIG. 2(a) or that of FIG. 3(a) can be calculated correctly, but notboth.

However, the delay circuit means for. correction of the base line for agentle curve as shown in FIG. 3 can not keep up with variations of thebase, line when the area of the peak on the negative slope as shown inFIG. 4 is calculated, whereby the error becomes considen able. FIG. 4shows changes of the peak and the base line with respect to the timeelapsed, in which the waveforms vary in the direction of the arrow astime passes. When the first peak is finished at time point B,

the point B of the figure becomes a base line; But the slope of thecurve to the start time point C of the second peak is so relativelysteep that the correction of the base line can not catch up with theslope. At the start time point C of the second peak, the base line iscorrected to a value before the time point C, for example, a value inthe time point E, whereby the area of the second peak becomes the areabetween E and F covered with the oblique lines, and is considerablysmaller than the actual peak area between the time point C and the timepoint D where the second peak actually begins and ends. Moreover, inpractical gas chromatography which employs gas as the mobile phase, thebase line of the detected signals is normally shifted all of a suddenfrom the high value X of the carrier gas to the low value Y of thesample gas, as shown in FIG. 5. Therefore, when the correcting operationfor the base line delayed by means of a delay control circuit issubjected to the detected signals of the carrier gas in gaschromatography, the first peak of the detected signals appearingadjacent to the turning point A at which the sample gas is mixed withthe carrier gas may be integrated on a false base line, i.e., the lineBE in FIG. 5, which is muchhigher than the real base line, i.e., theline B-C in FIG. 5, thereby reducing the detected area and givingmisleading information as to contents of the sample gas. Accordingly, itis necessary to carry out an instantaneous correcting operation for thebase line to follow the detected signals at once when the output of thebase line correcting device is detected to have negative polarity at theturning point.

An object of the present invention is to provide a base line correctingdevice wherein a exact correction of the base line can be carried outwith respect to any tion with preferred embodiments thereof withreference to the accompanying drawings, in which:

FIGS. 1(a) and 1(b) are schematic diagrams each showing examples waveforms of the signal for peak which is insufficiently separated fromadjacent peaks.

Another object of the present invention is to provide a base linecorrecting device for an integrator for chromatographical analysis,which is adapted to delay the start of the correcting operations for thebase line by means of a delay control circuit, which can select thedelay time after the end of the peak has been detected, to carry out acorrecting operation instantaneously for a very short time, unless thestart of the next peak is detected, after the delay time has elapsed,and to carry out the correcting operation for the base line with anordinary time lag after the very short time has been elapsed.

A further object of the present invention is to provide a system whereinthe slope is instantaneously corrected even when the slope of thenegative slope of the peak is steep, whereby the peak area on thenegative slope can be calculated more correctly. The instantaneouscorrection of the base line is carried out when the base line fallssteeply, while the correction of the base line is carried out with timelag, as before, on the other occasions. I

A still further object of the present invention is to provide a baseline correcting system for an integrator for chromatographical analysiswherein the polarity of the output of thebase line correcting device isdiscriminated, the correcting operation of the base line correctingdevice being carried out with a time lag when the polarity of the outputis positive or zero while the correcting operations of the base linecorrecting device are instantaneously carried out when the polarity ofthe output is negative.

These and other objects and features of the present invention willbecome apparent from the following full description of the presentinvention taken in conjuncchromatographical analysis, this diagram beingshown only for the purpose of illustration,

FIGS. 2(a) and 2(b) are schematic diagrams each showing another examplelike that of FIG. 1,

FIGS. 3(a) and 3(b) are schematic diagrams each showing a furtherexample like that of FIG. 1,-

FIGS. 4(a) and 4(b) are schematic diagrams each showings a still furtherexample like that of FIG. 1,

FIG. 5 is a schematic diagram showing a still further example like thatof FIG. 1,

FIG. 6 is a circuit block diagram showing a preferred embodiment of thepresent invention,

FIG. 7 is a circuit block diagram showing the details of part of FIG. 6,

FIG. 8 is a circuit block diagram showing another embodiment of FIG. 7,

FIG. 9 is a schematic diagram of a wave form shown only for the purposeof illustration, and

FIG. 10 is a schematic diagram of another wave form shown only forpurpose of illustration.

Considering the invention broadly, attention is directed to FIG. 6 whichillustrates a Gas Chromatography detector 10 in schematic block form forproviding an input signal to the device 11 of the present inventionwhich is the base line corrector. The signal from the detector 10 isamplified by a DC amplifier 12 which provides an input for two branchesof the circuit, i.e., to a peak detector 13 and the base line corrector11. The peak detector 13 indicates the existence of a peak in the signalfrom the detector 10 and maintains the peak indicating signal for aninterval of time beginning from the occurrence of the onset of theanalytical voltage fluctuation and ending at the termination of theanalytical fluctuation. The signal in the peak detector 13 serves as onemeans for informing the base line corrector 11 of the occurrence of thepeak so thatthe base line corrector 11 can withhold correction duringthe analytical fluctuation. The base line corrector 11 is adapted toco-operate with the input signal to correct the base line drift as willbe more throughly described hereinafter.

The output of the base line corrector 11 is supplied to digitalintegrator including a voltage-to-frequency converter 14, a gate 15 anda counter 16. The base line corrector 11 provides an input current tothe converter 14 to effect a drift correction in accordance with thepresent invention. The V-F converter 14 provides to the gate 15, anoutput in the form of pulses having a repetition rate proportional tothe amplitude of the input voltage. The gate 15 can be switched on totransfer the pulses from the converter 14 to the counter 16 when thepeak detector 13 detects the existence of a peak. The output of thecounter 16 for counting the number of the pulses is then fed to aprinter 17 which indicates the measured size of the peak. The base linecorrector 11 in the gas chromatograph is usually operated in the rangeof the low level signal the value of which is lower than that of athreshold level provided selectively in accordance with the samplinggas. The operation of the base line corrector 11 is illustrated more indetail in FIG. 7.

FIG. 7 is a block diagram showing one embodiment of the base linecorrecting device in accordance with the present invention. Referring toFIG. 7, 21 is a base line correcting device input to 'which signals fromthe chromatograph are provided, 22 being an amplifier, 23 being a baseline correcting device output, 24 and 25 being normally closed andnormally open contact points, respectively, for a relay which isdescribed later, and 26 being an amplifier or an integrator whichconsists of, for example, a resistor 27 with the resistance value of Rand a capacitor 28 with the capacity of C. The output signal of theamplifier 22 is supplied to the integrator 26 through the contact point24, and the input of the integrator 26 is fed back to the input side ofthe output of the amplifier 26. The contact point 25 is disposed inparallel with the resistor 27. 29 is a detector for the peak start, 30being a detector for the peak end, 31 being a flip-flop circuit which isset or reset by means of detectors 29 and 30, and 32 and 33 being relayseach of which is operated by means of the flip-flop 31 for closing thecontact points 24 and 25, respectively.

The amplifier 22 is provided with a signal from the chromatograph at theinput 21 thereof. When the contact point 24 is closed and the contactpoint 25 is open, the output 23 of the amplifier 22 is supplied to theintegrator 26 and the output of the integrator 26 is fed back to theinput side of the amplifier 22, whereby the output 23 is reduced zero.This is the correcting operation for the'base line, which, as long ascontact 24 is closed is continuously carried out with a time lagdetermined by the time constant of the resistance R and capacitance C ofthe integrator 26. It is well known that the correcting operation forthe base line is carried out with a time lag by negative feedback of theintegrator output t'o'the input side of the amplifier 22.

Next, the operations of the relay contacts 24 and 25 will be described.When the start of the peak is de tected by means of the detector 29, theflip-flop circuit 31 is set by the output thereof. At the setting by theoutput of the flip-flop circuit 31, the relay 32 is operated to open thecontact point 24. At this time, the relay 33 is not operated so that thecontact point 25 is maintained open. When the end of the peak isdetected by means of the detector 30, the flip-flop circuit 31 is resetwhereby the output disappears. At this time, the relay 32 holds thecontact point 24 for a fixed time which is a time lag, while the relay33 closes the contact point 25 for a very short time with the same timelag as in the relay 32.

FIG. 9 is a wave form of a chromatograph for illustrating the operationof the device shown in FIG. 7. Before the positive slope of the peak isdetected at point A, the contact point 24 in FIG. 7 is closed while thecontact point 25 is open, and the correcting operation for the base lineis carried out with a fixed time lag. When the start of the positiveslope 'of the peak has been detected at the point A, an output of thedetector 29 is provided to set the flip-flopfcircuit3l, and the relay 32opens the contact point 24 by the setting output of the flip-flopcircuit. Therefore, sincethe output of the amplifier 22 is not providedto the integrator 26, the correcting operation for the base line is notcarried out, whereby the value at the point A is retained. When the endof the peak is detected at point B, the flip-flop circuit 31 is reset bythe output of the detector 30. At this time, the relay 32 closes thecontact point 24 after a fixed time lag, which is the timeintervalcorresponding to the time between B and C of FIG. 9, and also, the

contact point 25 closes for a very short time. Accordingly, the contactpoint 24 remains closed during the very short time, and the resistor 27is short-circuited by the contact point 25, whereby the correctingoperation for the output 23 is carried out instantaneously. If theoutput 23 has diverged from the zero point, the output I 23 is correctedto zero instantaneously. After the correcting operation is completed,the contact point 25 opens while the contact point 24 remains closed.Ac-

cordingly, the correcting operation for the base line is carried outagain with the usual time lag until the point D at the start of thepositive slope of the next peak.

When the start of the next peak. has been detected by the detector 29between B and C, of FIG. 9, or during the delay time when the correctingoperation for the base line is not carried out after the end of one peakhas been detected, the contact point 24 is opened immediately by theoutput of the detector 29, whereby the instantaneous correctingoperation for the base line and the following ordinary correctingoperation are not carried out. The area of the second peak is integratedwith the same base line as that of the first peak.

The relay 33 comprising, for example, a delay circuit, a not circuit anda series circuit for a monostable multivibrator, can close the contactpoint 25 for a short time afterv a fixed delay'tirne when the settingoutput from the flip-flop disappears.

The present invention is designed asdescribed here- 'inbefore, so as todelay the start of the correcting operation for the base line during afixed time upondetection of the peak end, to carry out the instantaneouscorrecting operation for the base line during a very short time, unlessthe start of the next peak is detected during a fixed delay time, toinstantaneously correct the divergence of the base line during thedetection of the first peak and thereafter, to carry out the correctingoperation for the base line with the ordinary time lag. Thereforefif thetime interval, i.e., delay time, or the time between B and C of FIG. 9during which the correcting operation for the base line, after the endof the peak has been detected for peak as in FIG. 2(a), is not car riedout, is selected to be shorter than the time interval between B andC ofFIG. 2(a), theinstantaneous correcting operation for the base line canbecarried out at the point C of FIG. 2, whereby a correct calculation ofpeak'area can be carried out, as in FIG. 2(a), with respect to thesecond peak. If the second peak is wide and gentle, and the detection ofthe start of the peak is delayed (if thepeak of FIG. 1(b) is the secondpeak, and the first peak has ended prior thereto) as shownin FIG. 1(b),the instantaneous correcting operation for the base line is completed bypoint B, and the correcting operation for the base line is carried outwith the ordinary time lag at the point B. Thus, the shaded area of FIG.1(b) can be calculated correctly. I

On the other hand, if the time between B and C of FIG. 9 is selected tobe longer than the time between B and C of FIG. 3(a) for a peak as shownin FIG. 3(a), the correcting operation for the base line is not carriedout at all between, B and C of FIG. 3(a), whereby the area covered withoblique lines in FIG. 3(a) can be calculated correctly. The time betweenB and C of FIG. 9 can be changed at will by a change of the delay timeof the relays 32 and 33. Therefore, according to the present invention,the correct calculation of peak area can be carried out with respect toany chromatograph.

The start of the correcting operation for the base line after detectionof the end of the peak can be delayed by means of the flip-flop circuit31, and the relays 32 and 33. Since the delay time is variable, thecircuit comprising these elements 31, 32 and 33 has been called a delaycontrol circuit in view of the fact that the relay 32 opens the contactpoint 24 without the delay time upon detection of the peak start, butoperates with the delay time when the contact point 24 is closed.

FIG. 8 is a block diagram showing another example of the device inaccordance with the present invention, wherein 41 is an input terminalto which the signal from the chromatograph is provided, 42 being anamplifier, 43 being a feedback circuit for correcting the base line, 44being a polarity discriminating means, 45 being a relay having twocontacts 46 and 47, 48 being a switch, and 49 being an output terminal.

The circuit including the amplifier 42 and the feedback circuit 43, forcarrying out the correcting operation for the base line with the timelag, is known to those skilled in the art. In this case, the feedbackcircuit 43 is, for example, an integration circuit, the signal of outputside P of the amplifier 42 being fed back to the amplifier 42 as anegative feedback signal by the feed- I back circuit 43, whereby thesignal at point P is controlled to be zero. The signal supplied from thechromatograph through the terminal 41 appears at point P through theamplifier 42. It is well known that the signal of point P is controlledto zero with a fixed time lag to carry out the correcting operation forthe base line.

Also, a circuit for carrying out the correcting opera tion for the baseline by feeding the signal at P back to the amplifier 42 is also known.

Referring to FIG. 8, the signal at point P is fed through the feed-backcircuit 43 to the input side of the amplifier 42 with a fixed time lagwhen the contact point 46 of the relay 45 is closed, whereby the signalat point P is controlled to zero with a fixed time lag. On the otherhand, when the contact point 47 of the relay 45 is closed, the signal atpoint P is instantaneously controlled to zero. The switch 48 opens whena peak has'been detected. The correcting operation for the base line isnot carried out during a period in which the switch 48 is open, with theresult that the feedback from the feedback circuit to the amplifier ismaintained at a constant value.

The polarity discriminating device 44 detects the polarity of the signalat point P. The polarity of the signal which is applied to the inputterminal 41 negative slope, is negative, and the polarity of the signalat point P when the signal at point P has been shifted from zero by sucha signal is negative. The polarity discriminating device 44 closes thecontact point 46 of the relay 45 when the signal at the point P ispositive or zero, while the contact point 47 of the relay 45 closes whenthe signal at thepoint P is negative.

Referring to FIG. 10, the vertical axis shows the level of the signal atthe input terminal 41 and the signal at point P, while the horizontalaxis shows time. Assuming now that the signal (a) at the input terminal41 has been changed to the negative direction after the time point t thesignal (b) at the point P, which has been corrected with a fixed timelag, also changes to the negative direction, whereby the contact point47 of the relay 45 closes, and the contact point 46 thereof is opened bythe output of the polarity discriminating device 44. When the contactpoint of the relay 45 is switched to 47, the signal at the point P isinstantaneously fed back to the amplifier 42 through the feedbackcircuit 43 to instantaneously set the signal at the point P to zero. Atthe time point t the correction for the base line is instantaneouslycarried out to set the signal at the point P to zero, whereupon therelay 45 is switched to complete the circuit through thecontact point 46by the output of the discrimination circuit 44. At this time, the signalat point P is fed back to theamplifier 42 with a fixed time lag throughthe feed-back circuit 43. If the signal (a) at the input 41 stillremains in the negative direction, the signal at point P is changed tonegative again with the fixed time lag. At the time point t the relay 45is again switched to complete the circuit through the contact point 47by the discriminating circuit 44, whereby the signal at the point P isinstantaneously fed back to the amplifier 42 to again set the signal atpoint P to zero. Such operation is repeated so long as the signal (a) atthe input 41 is in the negative direction. Each time the signal at pointP is instantaneously set to zero, the instantaneous correcting operationfor the base line is carried out. The waveforms (b) of FIG. 10 show thesignals at the point P which have been corrected as describedhereinbefore.

The advantages obtainable by the present invention as described withreference to FIG.v 8 are described hereinafter with reference to FIG. 4(b). FIG. 4(b) shows the changes of the base line for the peaks as inFIG. 4(a) with respect to the time elapsed. At the point B, the outputof the amplifier 42 is zero, corresponding to t of FIG. 10. As theslope, corresponding to (a) of FIG. 10, of the negative slope from pointB of FIG. 4(b) to point C thereof, is corrected suchas shown by (b) inFIG. 10, the detection point C of the start ofthe second peak becomesthe base line for the second peak, whereby the area of the portiondefined by C, E, F and D covered with the oblique lines in FIG. 4(b) canbe calculated. It will be found that the error is'greatly reduced ascompared with the shaded portion defined by E and F in FIG. 4(a).

As described hereinbefore, in the present invention, the output thesignal, signal at point P of the amplifier 42 which receives the signalfrom the chromatograph, is fed back through a feed-back circuit 43. Theoutput signal of the amplifier 42 is set to zero to carry out thecorrecting operation for the base line of the integrator for thechromatograph, and the amplifier 42 and feedback circuit 43 carry outthe correcting operation for the base line as described hereinbefore.Therefore, they are hereinafter refered to as a base line correctingdevice. However, the output signal of the base line correcting deviceproduces an output signal of the amplifier 42 or the signal at the pointP. In this case, a circuit 44, which detects the polarity of the outputof the base line correcting device, decides whether the polarity of theoutput signal of the base line correcting device is negative or positiveor zero. When the polarity of the output signal of the base linecorrecting device is detected as being positive or zero by the thepolarity discriminating circuit, the correcting operation for the baseline is carried out with a fixed time lag, while,

when the polarity of the output signal of the base line correctingdevice is negative, the correcting operation for the base line isinstantaneously carried out. Accordingly, when the base line is shiftedin the positive direction, the correcting operation for the base line iscarried out by a conventional fixed-time-lag-system as de scribed withreference to FIG. 1(b). The correcting operation for the base line isinstantaneously carried out on the negative slope or when the base linesuddenly shifts in the negative direction due to a pressure change orthe like. Thus, the area under the peak can be calculated morecorrectly, even on the negative slope or when the base line suddenlyshifts in the negative direction. Although the present invention hasbeen fully described by way of example, various changes andmodifications will be apparent to those skilled in the art. Forexample,the correcting operations for the base line hereinbefore described inconnection with FIG. 8 are applied to the initial state of agaschromatographical measurement in which the base line is normallyshifted all of a sudden from the high value of the carrier gas to thelow value of the sample gas beyond the small value of the usual shiftsthereof. In addition, both means described as a first embodiment shownin N6. 7 and a second embodiment shown in FIG. 8 can be employedtogether so as to use properly either of the above two means inaccordance with the detected peak of the wave form, for example, in sucha manner that, when the wave form of signal has a plurality ofintegrated small peaks on the negative slope thereof, the first meansare employed with respect to the first smallpeak while the second meansare em ployed with respect to the other small peak. Also, the detailedconstruction of means 44 and 47 described in the second embodiment shownin FIG. 8 is the same as the construction of means 25, 26, 27 and 28described in the first embodiment shown in FIG. 7 as a unit.

What is claimed is: 1. An automatic base line drift corrector device foruse in an integrator for chromatographical analysis, comprising:

a. means for receiving a signal from a measuring instrument; b. peakdetecting means coupled to said signal receiving means for detecting thestart and end time points of a peak appearing in said signal, c.correction signal generating means coupled to said signal receivingmeans and said peak detecting d. first switching means coupled to saidcorrection signal generating means and said peak detecting means forswitching said correction signal generating means off between the startand end time points of a peak in said signal;

e. instantaneous correction signal means coupled to said correctionsignal generating means for causing instantaneous generation of acorrection signal;

f. time delay correction. signal'means coupled to said correction signalgenerating means for causing generation of a correction signal after apredetermined time delay;

g. further switching means coupled to said instantaneous correction onsignal means and said time delay correction signal means for switchingfrom one to the other for causing said correction signal generatingmeans to generate a correction signal instantaneously or with a timedelay at the end time point of a peak appearing in said signal; and

h. integrating means coupled to said correction signal generating meansand said peak detecting means for integrating the area under a peak inthe wave form of the signal.

2. An automatic base line drift corrector device as claimed in claim 1,in which said further switching means includes delay means for delayingthe operation of said further switching means for a certain period andafter said certain period, said further switching means switches saidinstantaneous correction signal means when the start time point has beendetected bysaid peakdetecting means and switches said time delaycorrection signal means when no starttim'e point has been detected. g

3. An automatic base line drift corrector device. asv claimed in'cla'im2 wherein said delaying means is operable to vary the certain period.

4. An automatic base line drift correctordevice as claimed in claim 1wherein said further switching means comprises discriminating means fordetecting the polarity of the wave form of the signal and for switchingsaid instantaneous correction signal means when the discriminating meansdetects a negative polarity and for switching said time delay correctionsignal means when the discriminating means detects a positive polarity.

5. An automatic base line drift corrector device as claimed in claim .4wherein said discriminating means is operable when fluctuations in thesignal are much larger than a predetermined value of drift.

1. An automatic base line drift corrector device for use in anintegrator for chromatographical analysis, comprising: a. means forreceiving a signal from a measuring instrument; b. peak detecting meanscoupled to said signal receiving means for detecting the start and endtime points of a peak appearing in said signal; c. correction signalgenerating means coupled to said signal receiving means and said peakdetecting means for generating a correction signal by which the baseline value of the signal can be carried out; d. first switching meanscoupled to said correction signal generating means and said peakdetecting means for switching said correction signal generating meansoff between the start and end time points of a peak in said signal; e.instantaneous correction signal means coupled to said correction signalgenerating means for causing instantaneous generation of a correctionsignal; f. time delay correction signal means coupled to said correctionsignal generating means for causing generation of a correction signalafter a predetermined time delay; g. further switching means coupled tosaid instantaneous correction on signal means and said time delaycorrection signal means for switching from one to the other for causingsaid correction signal generating means to generate a correction signalinstantaneously or with a time delay at the end time point of a peakappearing in said signal; and h. integrating means coupled to saidcorrection signal generating means and said peak detecting means forintegrating the area under a peak in the wave form of the signal.
 2. Anautomatic base line drift corrector device as claimed in claim 1, inwhich said further switching means includes delay means for delaying theoperation of said further switching means for a certain period and aftersaid certain period, said further switching means switches saidinstantaneous correction signal means when the start time point has beendetected by said peak detecting means and switches said time delaycorrection signal means when no start time point has been detected. 3.An automatic base line drift corrector device as claimed in claim 2wherein said delaying means is operable to vary the certain period. 4.An automatic base line drift corrector device as claimed in claim 1wherein said further switching means comprises discriminating means fordetecting the polarity of the wave form of the signal and for switchingsaid instantaneous correction signal means when the discriminating meansdetects a negative polarity and for switching said time delay correctionsignal means when the discriminating means detects a positive polarity.5. An automatic base line drift corrector device as claimed in claim 4wherein said discriminating means is operable when fluctuations in thesignal are much larger than a predetermined value of drift.